Pleasee...
Some of the issues you and other mention (check The Hull Truth, lol) are pretty specific to jet drives used in outboards' lower units, which is a completely different situation that Yamaha jb hamiltons so let's not confuse those. The hamiltons (like our pumps) are volume pumps and will carry a much heavier load then say an american turbine which is a pressure pump, and get way, way better fuel economy. All boat propulsion systems are sensitive to engine and propulsion unit mismatch, jet or propeller mismatch alike results in poor performance and inefficient fuel consumption, but the jet drives attached to outboards are usually not well matched at all.
The jet pump advantages are indisputable in most categories:
"Zero speed - maximum thrust" ascertain absolutely superior acceleration and steering, and "power breaking" ability, too.
The reverse is exellent on our pumps compared to stern or V-drives!!! And so is maneuverability, with no transmission you can do just about anything with them at any throttle setting.
The fuel efficiency and performance of a jetboat can be affected by anything that disrupts the smooth flow of water through the jet unit. Not just a plastic bag sucked onto the jet unit's intake grill, but inefficient sealing of the tunnel or pump segments can have quite an adverse effect.
Yes, unfortunately, Yamaha sucks where is comes to QC, but their engine/drive/pump design is superb: simple and efficient (when properly setup, tuned and maintained).
Plus of course all the other advantages of jet drives like safety and shallow water capability.
Jet disadvantages are there, too:
Wet splitting is iffy, so if I had to wet slip in the ocean I would 100% chose an o/b.
No lifting strakes or chines or stepped hull possible due to intakes under hull sucking air.
Clogging in algae infested waters etc.
EDIT: as far as the noise - it is totally dependent on how you want to deal with it. In my case, it took a while and a lot of effort but my AR240 is QUIETER than most of my friends inboards. Fact.
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